Intramolecular [4 + 2] Cycloaddition Reactions of Diarylacetylenes: Synthesis of Benzo[b]fluorene Derivatives via Cyclic Allenes

• DOI: 10.1021/ol991391t
• Publication Date: 2002-07-26T06:06:24Z
• Authors: David Rodríguez; Armando Navarro; Luis Castedo; Domingo Domínguez; Carlos Saá
• Keywords: Allene

2-Propynyldiarylacetylenes undergo thermal intramolecular [4 + 2] cycloaddition to give benzo[b]fluorene derivatives in good yields. The hybridization of the tether connecting reacting alkynes has a pronounced effect on course reaction. Theoretical calculations and isotopic labeling studies support mechanism which involves generation cyclic allene intermediate that evolves final benzo[b]fluorene.